Multi-disc wet brakes are well known in the art of braking systems and are available with a variety of actuation mechanisms. Such multi-disc wet brakes employ a disc assembly having plurality of alternating stationary and rotating discs to generate a braking force. The stationary discs are rotationally secured to a pin or other object within the brake housing to prevent rotation thereof, whereas the rotating discs are rotationally engaged with a shaft, the shaft itself being rotationally coupled to a vehicle axle. During normal operating conditions, rotation of the shaft causes rotation of the rotating discs. A clearance is provided between each rotating disc and the adjacent stationary discs to facilitate such rotation, thereby allowing the vehicle to move freely. When the brake is actuated, an actuating mechanism acts upon a primary stationary disc to compress the disc assembly, thereby creating friction at each interface between a rotating disc and a stationary disc. This friction created within the disc assembly acts as a braking force to first slow, and ultimately stop, rotation of the rotating discs. A fluid is provided within the brake housing to absorb the heat generated by the friction between discs during braking conditions, thereby cooling and improving the efficiency of the brake.
A common problem associated with multi-disc wet brakes relates to actuation of the brake to compress the alternating stationary and rotating discs of the disc assembly. A hydraulic slave cylinder is often provided as an actuating mechanism, and includes a piston and a piston rod that, when actuated, acts upon the primary stationary disc either directly or indirectly to compress the disc assembly. However, due to the clearance provided on either side of each of the rotating discs during normal operation of the vehicle, the piston of the slave cylinder must have a relatively long stroke in order to take up the total clearance within the disc assembly.
The increased piston stroke necessary to actuate conventional multi-disc wet brake results in at least two significant disadvantages. One such disadvantage is an increased response time of the brake due to the time it takes for the piston to take up the running clearance within the disc assembly. Little braking force is generated by the disc assembly until all of the running clearances between the stationary and rotating discs have been eliminated. Thus, a time delay occurs between the initial actuation of the slave cylinder and the time when a braking force acts upon the rotating shaft. Another disadvantage is the volume of brake fluid necessary to effect the increased piston stroke. The volume of fluid provided by the master cylinder to the slave cylinder is frequently insufficient to generate the piston stroke needed in multi-disc wet brakes. The conventional solution to this problem is to add a power booster to the brake system, which is not cost effective.
Thus, the need exists for a multi-disc wet brake having a slave cylinder that provides an improved response time and requires a relatively smaller amount of brake fluid for actuation of the multi-disc wet.